An improved model for the effect of correlated Si-III absorption on the one-dimensional Lyman-$α$ forest power spectrum
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arXiv
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| Format: | Preprint |
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2025
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| author | Ma, Ke Bolton, James S. Irsic, Vid Gaikwad, Prakash Puchwein, Ewald |
| author_facet | Ma, Ke Bolton, James S. Irsic, Vid Gaikwad, Prakash Puchwein, Ewald |
| contents | We present an analysis of Si III absorption and its effect on the 1D Ly$α$ forest power spectrum using the Sherwood-Relics hydrodynamical simulation suite. In addition to oscillations from the Ly$α$--Si III cross correlation that are damped toward smaller scales, we find an enhancement in small-scale power that has been ignored in previous studies. We therefore develop a new analytical fitting function that captures two critical effects that have previously been neglected: distinct Ly$α$ and Si III line profiles, and a variable ratio for coeval Ly$α$ and Si III optical depths. In contrast to earlier work, we also predict amplitudes for the Si III power spectrum and Ly$α$--Si III cross power spectrum that decrease toward lower redshift due to the hardening metagalactic UV background spectrum at $z\lesssim 3.5$. The fitting function is validated by comparison against multiple simulated datasets at redshifts $2.2\leq z \leq 5.0$ and wavenumbers $k < 0.2\rm\,s\,km^{-1}$. Our model has little effect on existing warm dark matter constraints from the Ly$α$ forest when adopting a physically motivated prior on the silicon abundance. It will, however, be an essential consideration for future, high precision Ly$α$ forest power spectrum measurements. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_08613 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | An improved model for the effect of correlated Si-III absorption on the one-dimensional Lyman-$α$ forest power spectrum Ma, Ke Bolton, James S. Irsic, Vid Gaikwad, Prakash Puchwein, Ewald Cosmology and Nongalactic Astrophysics We present an analysis of Si III absorption and its effect on the 1D Ly$α$ forest power spectrum using the Sherwood-Relics hydrodynamical simulation suite. In addition to oscillations from the Ly$α$--Si III cross correlation that are damped toward smaller scales, we find an enhancement in small-scale power that has been ignored in previous studies. We therefore develop a new analytical fitting function that captures two critical effects that have previously been neglected: distinct Ly$α$ and Si III line profiles, and a variable ratio for coeval Ly$α$ and Si III optical depths. In contrast to earlier work, we also predict amplitudes for the Si III power spectrum and Ly$α$--Si III cross power spectrum that decrease toward lower redshift due to the hardening metagalactic UV background spectrum at $z\lesssim 3.5$. The fitting function is validated by comparison against multiple simulated datasets at redshifts $2.2\leq z \leq 5.0$ and wavenumbers $k < 0.2\rm\,s\,km^{-1}$. Our model has little effect on existing warm dark matter constraints from the Ly$α$ forest when adopting a physically motivated prior on the silicon abundance. It will, however, be an essential consideration for future, high precision Ly$α$ forest power spectrum measurements. |
| title | An improved model for the effect of correlated Si-III absorption on the one-dimensional Lyman-$α$ forest power spectrum |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2509.08613 |